The present invention relates to the inclusion of lipid-enriched, hydrophobic compositions with improved stability on the bodyfacing materials of disposable absorbent articles, such as diapers, training pants, adult incontinence products, underpants, feminine care products, nursing pads, wound dressings and similar articles having absorbent capacity. The present invention also relates to improving skin health by protecting and enhancing the barrier function of the skin through delivery of hydrophobic compositions from the bodyfacing materials of disposable absorbent articles to the skin. Prior to delivery to the skin, the compositions are stable on the bodyfacing materials. The compositions of the invention can also provide benefit to the barrier function of the skin when they are incorporated into other skin-contacting materials such as tissues, wet wipes and cosmetic cleansing or buffing pads.
The stratum corneum is the outer-most layer of the skin and is responsible for regulating skin water levels and functioning as a barrier against chemicals and other stress agents found in the environment. The complex arrangement of lipids in the intercellular space of the stratum corneum is responsible for the establishment of normal barrier function. Multi-layered structures of cholesterol, ceramides and fatty acids, as well as some other minor lipids, provide the major barrier to the transport of substances into or through the skin. The overall structure of the stratum corneum acts as the frontline barrier to the skin. The link between skin barrier function and skin health is apparent from the skin inflammation caused by lipid extraction from the skin. That is, when skin barrier function is impaired, the other layers of the skin can be injured and have a response to that injury in the form of inflammation.
In the area of skin health, it is known to apply lipid-containing compositions to the skin in order to enhance the barrier function of the stratum corneum. This approach is disclosed in U.S. Pat. No. 5,643,899 issued to Elias et al. on Jul. 1, 1997. For some time, those of skill in the art have believed that it is necessary to apply all three of the lipid components of the stratum corneum (cholesterol, ceramides and fatty acids) to the skin in order to replenish and repair the skin and in order to not affect the normal repair processes of the skin. In particular, ceramides are believed to be very important. In fact, the art teaches that if fewer than all three of the components are used in a skin composition, the composition could actually compromise or delay repair of the barrier.
In U.S. patent application Ser. No. 09/379,928 filed Aug. 24, 1999, various compositions for improving skin health are described, including compositions suitable for use in conjunction with absorbent articles. The compositions in patent application Ser. No. 09/379,928 were found to provide benefits for skin health. The compositions were described as containing a variety of potential components and, in some forms, the compositions included natural fats and oils, sterols and sterol derivatives, humectants and surfactants. These compositions have been found to improve skin health even though they do not necessarily include any ceramides. Efficacy without ceramides was unexpected. Though the exact mechanism of functionality was not known, one hypothesis was that an emulsion of the lipid components (natural fats/oils and sterols/sterol derivatives) was formed in the humectant component (through the use of a surfactant). In some of the embodiments that were described, the humectant was glycerin. Incorporation of such an emulsion into an ointment formulation was predicted to be more easily absorbed or taken up by the skin. The ointment formulation, which could include petrolatum, would form an occlusive film on the skin, thereby trapping water between the skin and the occlusive film. The trapped water was predicted to facilitate uptake of the emulsion and, therefore, the natural fats/oils and sterols, by the skin. Therefore, the humectant and surfactant components of the compositions were perceived to be facilitating the transfer of the lipid components to the skin.
Therefore, benefits and improvements to skin health have been observed when compositions containing the lipids naturally present in the stratum corneum are applied to the skin. Though the exact mechanisms are not known, one hypothesis is that the lipids being applied with the compositions are replenishing lipids that have been lost from the stratum corneum as a result of physical or biological insults. Another hypothesis is that the lipids being applied with the compositions are providing additional lipids to the stratum corneum resulting in better protection against insults. The stratum corneum of the skin is constantly exposed to physical and biological insults that could have a negative effect on barrier function.
Absorbent articles such as diapers, training pants, incontinence products and feminine care products are worn such that they are in direct contact with the skin of the wearer. An unavoidable consequence of the use of absorbent articles is that the skin is exposed more directly to various physical and biological insults. Consequently, the barrier function of the skin covered by the absorbent article is put at risk. In order to provide disposability, absorbent articles are primarily constructed of nonwoven materials. Even though nonwoven materials are engineered to have soft hand and drape, they rub against the skin and there is friction. Such friction constitutes one form of physical insult to the skin barrier. Friction against the skin barrier also occurs with the use of absorbent tissues and wipes. Absorbent tissue and wipe products are frequently used for cleansing the skin areas covered by absorbent articles. Absorbent tissue and wipe products are necessary for removing biological waste materials from the skin.
In addition to these physical insults, skin covered by absorbent articles is also frequently exposed to biological insults. Biological fluids, such as urine, feces, vaginal secretions and nasal secretions, may contain a variety of components that can damage the skin barrier. Examples of these components include proteases, lipases and bile acids. Once the skin barrier is compromised, these components, in addition to other constituents of biological fluids, can initiate or exacerbate inflammation of the skin.
Diaper dermatitis is a genre of skin conditions that, in large part, originate from impaired skin barrier function. Impairment of the skin barrier can result from a variety of factors, including: increased skin hydration due to the occlusion of the skin caused by diapers, enzymatic skin damage due to fecal and urinary enzymes, and physical damage caused by friction against the diaper surface and repeated cleaning of the skin with absorbent tissues or wet wipes.
Excessive hydration of the skin also has a negative effect on the skin barrier. The hydration level of diapered skin, for example, may reach between five to ten times that of undiapered skin. Frequent contact of diapered skin with urine may also contribute to increased skin hydration. Increased skin hydration disrupts skin lipid organization in the stratum corneum. This disruption may increase the permeability of the skin to irritants from feces and urine, thus increasing the risk of skin inflammation.
Disposable absorbent articles such as diapers, training pants, adult incontinence products, absorbent under pants, feminine care products and nursing pads have been used to absorb body fluids and leave the skin dry. Disposable absorbent articles of this type generally include a liquid impermeable backsheet member, an absorbent core or assembly, and a liquid permeable body facing or liner material. The body facing or liner material comes into contact with the wearer""s skin. While the body facing material is made of a soft, compliant material, the material rubs against the skin during use and may not leave the skin completely dry and free of the bodily fluids, such as solid or semi-solid waste, the absorbent article is trying to absorb. During frequent insults of bodily fluids and frequent use of disposable absorbent articles, the skin can become irritated and appear red and be sore to the touch.
Creams, lotions or ointments can be used to provide an artificial hydrophobic barrier on the skin and to treat skin conditions such as diaper rash. Application of these types of products to the skin is often messy and inconvenient. Often, these products are not used prophylactically and are only used when signs of diaper rash are visible.
Diaper liners and other bodyfacing materials may be treated with emollients, such as petrolatum, that can be transferred to the skin through normal diapering practices. Once transferred to the skin, diaper liner formulations may provide an artificial barrier against feces and urine. These formulations may require high concentrations of petrolatum to ensure sufficient transfer to the skin to provide a benefit. High concentrations of petrolatum can be messy, greasy to the touch, and may impair the fluid handling properties of an absorbent article, such as a diaper. The slow penetration of petrolatum into the skin can lead to smearing of the agent over the skin and onto clothes and other materials.
Formulations, such as those containing petrolatum, are applied to the bodyfacing materials of absorbent articles during manufacture. In order to process and apply the formulations to the bodyfacing materials, the formulations need to be in a semi-solid or fluid state. However, in order to have stability on the bodyfacing material after manufacture, the formulations need to be semi-solid or solid across a wide range of shipping and storage temperatures. Not all of the presently known formulations are sufficiently stable on the bodyfacing materials. Consequently, such formulations may transfer off of the bodyfacing material prematurely or the formulations may migrate away from the skin-facing surfaces of the materials.
Thus, what is needed is a topically effective composition delivered from a bodyside or bodyfacing material of an absorbent article that protects, maintains, recovers or otherwise benefits skin barrier function against physical damage and irritants in biological fluids. It would also be desirable to provide a topical composition delivered from a bodyside material of an absorbent article that absorbs into the skin, is non-greasy and cosmetically acceptable to the consumer. Additionally, it would be desirable to provide a topical composition having improved stability on the bodyside material of an absorbent article. Further, it would be desirable to provide a topical composition delivered from a bodyside material of an absorbent article that does not impair the waste containment functions of the absorbent article.
In response to the difficulties and problems discussed above, compositions and the use of those compositions on absorbent articles for improving the barrier function of the skin have been discovered. The compositions of the invention provide several benefits associated with barrier function including protecting, strengthening, restoring and repairing the skin barrier. While the compositions of the inventions can have a variety of applications, the compositions are particularly beneficial when used in conjunction with absorbent articles such as diapers, incontinence garments, feminine care products, training pants, diaper pants, nursing pads and wound dressings. Additionally, the compositions of the invention could also provide benefits when used in conjunction with tissue, pre-moistened wipe products and cosmetic cleansing and buffing pads. A further benefit of the compositions of the invention is that the compositions show improved stability during processing and application to an article. The purposes and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by practice of the invention. Additional advantages of the invention will be realized and attained by the compositions and articles particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
In one aspect, the present invention relates to an absorbent article that includes an outer cover, a bodyside liner, an absorbent body and a composition. The bodyside liner is typically liquid permeable and defines a bodyfacing surface. The bodyside liner is connected in a generally superposed relation to the outer cover. The absorbent body is located between the bodyside liner and the outer cover. The composition is on a portion or the entire bodyfacing surface of the bodyside liner. The composition can be generally solid, semi-solid or liquid. The composition may be in a variety of forms, including, but not limited to, emulsions, lotions, creams, ointments, salves, suspensions, gels and the like. The composition can be applied to the bodyside liner using a variety of techniques including foam application, spraying, slot coating and printing. The present invention also encompasses technology that would permit integration of the composition directly with fibers or other materials used to form the bodyside liner. The compositions can be applied to the bodyfacing surface in amounts of from about 0.1 grams per meter squared (g/m2) to about 30 g/m2.
The compositions of the invention could also be applied to or be present on other skin contacting surfaces of absorbent articles such as the waist and leg elastics and the containment flaps. The compositions include from about 0.1 to about 95 percent by weight of natural fats or natural oils. More specifically, the compositions can include from about 5 to about 75 percent by weight of natural fats or natural oils. Desirably, the compositions of the invention include from about 10 to about 50 percent by weight of natural fats, natural oils or mixtures of both. Natural fats and oils include fats, oils, essential oils, fatty acids, fatty alcohols, phospholipids and mixtures of these compounds. The natural fats and oils can be similar to the lipids that are present in healthy skin in order to mimic the naturally present lipids. Synthetic or synthetically modified fats and oils could potentially also be used if they functioned in the same manner as their natural counterparts. Examples of fats and oils include Avocado Oil, Apricot Oil, Babassu Oil, Borage Oil, Camellia Oil, Canola Oil, Castor Oil, Coconut Oil, Corn Oil, Cottonseed Oil, Evening Primrose Oil, Hydrogenated Cottonseed Oil, Hydrogenated Palm Kernel Oil, Maleated Soybean Oil, Meadowfoam Oil, Palm Kernel Oil, Peanut Oil, Rapeseed Oil, Safflower Oil, Sphingolipids, Sweet Almond Oil, Tall Oil, Lanolin, Lanolin Alcohol, Lauric Acid, Palmitic Acid, Stearic Acid, Linoleic Acid, Stearyl Alcohol, Lauryl Alcohol, Myristyl Alcohol, Behenyl Alcohol, Rose Hip Oil, Calendula Oil, Chamomile Oil, Eucalyptus Oil, Juniper Oil, Sandlewood Oil, Tea Tree Oil, Sunflower Oil, Soybean Oil and mixtures thereof.
The compositions also include sterols, sterol derivatives or mixtures of both in an amount of from about 0.1 to about 10 percent by weight. Sterols and sterol derivatives include compounds such as xcex2-sterols with a tail on the 17 position and no polar groups, such as cholesterol, C10-C30 cholesterol/lanosterol esters, tall oil sterols, soy sterols, sterol esters and mixtures of these compounds. More specifically, the compositions include from about 0.5 to about 5 percent by weight of sterols, sterol derivatives or mixtures of both. Even more specifically, the compositions include from about 0.8 to about 1 percent by weight of the sterol compounds. Examples of suitable sterol compounds include cholesterol, sitosterol, stigmasterol, and ergosterol, as well as, C10-C30 cholesterol/lanosterol esters, cholecalciferol, cholesteryl hydroxystearate, cholesteryl isostearate, cholesteryl stearate, 7-dehydrocholesterol, dihydrocholesterol, dihydrocholesteryl octyldecanoate, dihydrolanosterol, dihydrolanosteryl octyldecanoate, ergocalciferol, tall oil sterol, soy sterol acetate, lanasterol, soy sterol, avocado sterols, xe2x80x9cAVOCADINxe2x80x9d (available from Croda Ltd. of Parsippany, N.J.), sterol esters and mixtures thereof.
The compositions of the invention further include from about 1 to about 95 percent by weight of one or more emollients. More specifically, the compositions include from about 20 to about 75 percent by weight of emollient(s). Even more specifically, the compositions include from about 40 to about 60 percent by weight of emollient(s). Suitable emollients include petroleum based oils, petrolatum, vegetable oils, mineral oils, alkyl dimethicones, alkyl methicones, alkyidimethicone copolyols, phenyl silicones, alkyl trimethylsilanes, dimethicone, lanolin and its derivatives, fatty esters, glycerol esters and their derivatives, propylene glycol esters and their derivatives, alkoxylated carboxylic acids, alkoxylated alcohols, fatty alcohols and mixtures of such compounds.
The compositions of the invention also include from about 5 to about 95 percent by weight of one or more solidifying agents. More specifically, the compositions include from about 25 to about 75 percent by weight of solidifying agents. Even more specifically, the compositions include from about 30 to about 50 percent by weight of solidifying agents. A solidifying agent is a material capable of solidifying the composition so that the composition is solid at room temperature and has a penetration hardness of at least 5 mm. More specifically, the solidifying agent includes one or more materials that are capable of solidifying the natural fats/oils and emollient combination so as to have a penetration hardness of 5 to about 365 mm at 25xc2x0 C. Further, the solidifying agent solidifies the fat/oil/emollient combination so that it has a melting point between 32xc2x0 C. and 100xc2x0 C. One or more solidifying agents can be selected from alkyl siloxanes (with a melting point greater than 35xc2x0 C.), polymers, waxes (animal, vegetable or mineral), hydrogenated vegetable oils having a melting point of 35xc2x0 C. or greater and fatty acid esters having a melting point of 35xc2x0 C. or greater.
Examples of suitable solidifying agents include, but are not limited to, the following compounds: alkyl silicones, alkyl trimethylsilanes, beeswax, C24-C28 alkyl dimethicone, C30 alkyl dimethicone, cetyl methicone, stearyl methicone, cetyl dimethicone, stearyl dimethicone, cerotyl dimethicone, candelilla wax, carnauba, cerasin, hydrogenated microcrystalline wax, jojoba wax, microcrystalline wax, lanolin wax, ozokerite, paraffin, cetyl esters, behenyl behenate, C20-C40 alkyl behenate, C12-C15 lactate, cetyl palmitate, stearyl palmitate, isosteryl behenate, lauryl behenate, stearyl benzoate, behenyl isostearate, cetyl myristate, cetyl octanoate, cetyl oleate, cetyl ricinoleate, cetyl stearate, decyl oleate, di-C12-C15 alkyl fumerate, dibehenyl fumerate, myristyl lactate, myristyl lignocerate, myristyl myristate, myristyl stearate, lauryl stearate, octyldodecyl stearate, octyidodecyl stearoyl stearate, oleyl arachidate, oleyl stearate, tridecyl behenate, tridecyl stearate, tridecyl stearoyl stearate, pentaerythrityl tetrabehenate, pentaerythritylhydrogenated rosinate, pentaerythrityl distearate, pentaerythrityl tetraabeite, pentaerythrityl tetracocoate, pentaerythrityl tetraperlargonate, pentaerythrityl tetrastearate, ethylene vinyl acetate, polyethylene, hydrogenated vegetable oil, hydrogenated squalene, hydrogenated coconut oil, hydrogenated jojoba oil, hydrogenated palm oil, hydrogenated palm kernel oil, hydrogenated olive oil, polyamides, metal stearates and other metal soaps, C30-C60 fatty alcohols, C20+ fatty amides, polypropylene, polystyrene, polybutane, polybutylene terephthalate, polydipentane, polypropylene, zinc stearate and mixtures of such compounds.
In addition to the components already described, the compositions of the invention may further include from about 0.1 to about 25 percent by weight of one or more compounds acting as viscosity enhancers. More specifically, the compositions include from about 5 to about 20 percent by weight of one or more viscosity enhancers. Even more specifically, the compositions include from about 10 to about 15 percent by weight of viscosity enhancer(s). The viscosity enhancer increases the meltpoint viscosity of the compositions to have a high viscosity at the xe2x80x9chot box carxe2x80x9d stability temperature of approximately 54.5xc2x0 C. Having high viscosity at elevated temperatures prevents the compositions from migrating into or away from the materials to which they are applied. However, the viscosity enhancer component also provides a low viscosity ( less than 200 centipoise) for the compositions at process temperatures. Typically, process temperatures are approximately 5xc2x0 C. above the melting point of the composition. Examples of suitable viscosity enhancers include polyolefin resins, lipophilic/oil thickeners, ethylene/vinyl acetate copolymers, polyethylene, silica, silica silylate, silica methyl silylate, colloidal silicone dioxide, alkyl hydroxy ethyl cellulose, other organically modified celluloses, PVP/decane copolymer, PVM/MA decadiene crosspolymer, PVP/eicosene copolymer, PVP/hexadecane copolymer and mixtures of these compounds.
In addition to one or more viscosity enhancers, the compositions of the invention may also include one or more rheology modifiers. Rheology modifiers are compounds that increase the viscosity of the compositions at lower temperatures as well as process temperatures. Rheology modifiers are also compounds that provide xe2x80x9cstructurexe2x80x9d to the compositions to prevent settling out (separation) of insoluble and partially soluble components. By increasing the viscosity at process temperatures, the rheology modifiers will increase the viscosity above 200 centipoise. However, the rheology modifiers are thixotropic in behavior; therefore, their viscosity decreases as shear and pressure increases. Consequently, when the rheology modifiers are used in the compositions of the invention, they maintain the suspension of insoluble and partially soluble components. This capability can be particularly important if, during processing, the composition must be left stagnant in process lines and hoses. The rheology modifiers will maintain the suspension of the insoluble and partially soluble components for a period of time that depends on the viscosity of the composition and on the amount of rheology modifier present. The thixotropic behavior of the rheology modifiers causes their viscosity to drop when processing is resumed and the composition is no longer stagnant due to the application of pressure and shear forces. In addition to stabilizing the suspension of insoluble and partially soluble components, the rheology modifiers of the invention also help to stabilize the compositions on the bodyfacing or other materials to which the compositions are applied. Examples of suitable rheology modifiers include silica, silica silylate, silica methyl silylate, quaternary starch compounds and mixtures thereof. Such rheology modifiers can help maintain the suspension of a partially soluble emollient, such as a siloxane, within the composition. The compositions of the invention can include from about 0.5 to about 5 percent by weight of one or more rheology modifiers.
The stability of the compositions of the invention can also be improved through the use of one or more alkyl silicones as one of the solidifying agents in the composition. Alkyl silicones have been found to facilitate the homogenous incorporation of some emollients, such as siloxanes, into the hydrocarbon-based compositions of the invention. The ability of alkyl silicones to stabilize siloxanes (silicones) was unexpected given the inherent incompatibility of siloxanes with oils such as may be used in the compositions of the invention. The inherently high molecular weights of alkyl silicones are believed to be a factor in their role as solidifying agents. Additionally, the alkyl silicones are believed to act as coupling agents for the siloxanes with the organic phase of the composition which may include fats/oils, waxes or petrolatum. The ability of alkyl silicones to couple the siloxane and organic phases of the composition is due to the alkyl functionality incorporated into the siloxane molecule. Thus, by possessing both silicone and alkyl functionalities in the same molecular structure, physically stable siloxane/hydrocarbon compositions can be achieved. The alkyl silicones are able to maintain the homogeneity of the siloxanes in the compositions even at higher temperatures, such as may be experienced during processing, where the absence of the alkyl silicone will result in severe phase separation of the siloxane from the composition. Typically, alkyl silicones having a high molecular weight (C12 or greater, or a high degree of alkyl substitution) are desirable for the compositions of the invention. Siloxanes having a high degree of polymerization are also desirable. The compositions of the invention can include from about 0.5 to about 30 percent by weight of one or more siloxanes, such as dimethicone. Additionally, the compositions of the invention can include from about 0.5 to about 30 percent by weight of one or more alkyl silicones.
As will be described later in further detail, the compositions of the invention have been shown to enhance the barrier function of the stratum corneum of the skin. The presence of the compositions of the invention on the skin, when the skin is subjected to physical and biological insults, has been shown to be beneficial. Though the exact mechanism(s) is not known, it is possible that the compositions of the invention provide a superior barrier that prevents the skin from uptaking moisture. Based on the hypothesis that emulsions of lipid components (fats and oils/sterols) in a humectant facilitate the transfer of lipids to the skin, it was unexpected that compositions having no water soluble components could enhance the barrier function of the skin. Without water soluble components, it was believed that there would be no mechanism to facilitate transfer of the fats, oils and sterols to the skin.
In addition to the components already described, the compositions of the invention may also include active ingredients such as those ingredients that may be useful for treating skin irritations such as diaper rash. Examples of such active ingredients include allantoin and its derivatives, aluminum hydroxide gel, calamine, cocoa butter, cod liver oil, dimethicone, glycerin, kaolin and its derivatives, lanolin and its derivatives, mineral oil, petrolatum, shark liver oil, talc, topical starch, zinc acetate, zinc carbonate, zinc oxide and mixtures of these ingredients. Some of the ingredients listed as possible active ingredients for treating the skin can also be used as emollients.
In order to enhance or increase the function of the compositions of the invention, additional ingredients may be added. Examples of the classes of ingredients along with their functions include: antifoaming agents (reduce the tendency of foaming during processing); antimicrobial actives; antifungal actives; antiseptic actives; antioxidants (product integrity); antioxidants-cosmetic (reduce oxidation); astringents-cosmetic (induce a tightening or tingling sensation on skin); astringent-drug (a drug product that checks oozing, discharge, or bleeding when applied to skin or mucous membrane and works by coagulating protein); biological additives (enhance the performance or consumer appeal of the product); colorants (impart color to the product); deodorants (reduce or eliminate unpleasant odor and protect against the formation of malodor on body surfaces); other emollients (help to maintain the soft, smooth, and pliable appearance of the skin by their ability to remain on the skin surface or in the stratum corneum to act as lubricants, to reduce flaking, and to improve the skin""s appearance); external analgesics (a topically applied drug that has a topical analgesic, anesthetic, or antipruritic effect by depressing cutaneous sensory receptors, or that has a topical counterirritant effect by stimulating cutaneous sensory receptors); film formers (to hold active ingredients on the skin by producing a continuous film on skin upon drying); fragrances (consumer appeal); silicones/organomodified silicones (protection, tissue water resistance, lubricity, tissue softness); oils (mineral, vegetable, and animal); natural moisturizing agents (NMF) and other skin moisturizing ingredients known in the art; opacifiers (reduce the clarity or transparent appearance of the product); powders (enhance lubricity, oil adsorption, provide skin protection, astringency, opacity, etc.); skin conditioning agents; solvents (liquids employed to dissolve components found useful in the cosmetics or drugs); and surfactants (as cleansing agents, emulsifying agents, solubilizing agents, and suspending agents).
Ranges are used to describe the relative quantities of compounds in the compositions of the invention and ranges are used to describe the relative physical properties of the compositions of the invention. It is understood that the ranges are by way of illustration only and that one of skill in the art would recognize that the nature of the specific compositions dictates the levels to be applied to achieve the desired results. The levels of components are ascertainable by routine experimentation in view of the present disclosure.
The compositions of the invention typically have a melting point of from about 32xc2x0 C. to about 100xc2x0 C. Melting behavior in this range provides compositions that are relatively immobile and localized on the bodyfacing surface of the bodyside liner of the absorbent article at room temperature. Though relatively immobile and localized at room temperature, the compositions are also readily transferable to the wearer of the article at body temperature through natural rubbing or friction during wearing and through adhesion of the composition to the skin of the wearer. The compositions also maintain their integrity and are not completely liquid at elevated temperatures such as may be experienced during storage. Stability in a solid state at elevated temperatures is made possible, in part, to the increase in viscosity provided by the viscosity enhancers. Desirably, the compositions of the invention are easily transferable to the skin by way of normal contact, including adhesion of the composition to the skin, wearer motion or body heat. Because the compositions are relatively immobilized on the bodyfacing surfaces of the articles, the quantities of the compositions necessary to provide the desired skin barrier benefits are reduced. In addition, special barrier or wrapping materials may not be necessary for the articles of the invention.
The compositions of the invention have viscosities that range from about 10 to about 10,000 centipoise as measured at a temperature of 60xc2x0 C. At 55xc2x0 C., the compositions have viscosities from about 200 centipoise to about 100,000 centipoise. The compositions may also have a penetration hardness of from about 5 millimeters to about 365 millimeters at 25xc2x0 C.
In addition to the articles and compositions already described, the present invention is also directed to absorbent articles that include an outer cover, a liquid permeable bodyside liner, an absorbent body and a composition on at least a portion of the bodyside liner. The bodyside liner defines a bodyfacing surface and the bodyside liner is connected in superposed relation to the outer cover. The absorbent body is located between the bodyside liner and the outer cover. The composition is on at least a portion of the bodyfacing surface of the bodyside liner.
The composition can include from about 0.5 to about 75 percent by weight of natural fats or oils. The natural fats and oils may be selected from avocado oil, borage oil, sunflower oil, soybean oil, corn oil, cottonseed oil and mixtures of such fats and oils. The composition can also include from about 0.5 to about 5 percent by weight of sterols and sterol derivatives. The sterols and sterol derivatives may be selected from cholesterol, sitosterol, stigmasterol, tall oil sterol, soy sterol and mixtures of such sterols. Additionally, the composition can include from about 20 to about 75 percent by weight of one or more emollients. The emollients may be selected from petrolatum, silicone oils, dimethicone, lanolin and mixtures of such emollients. The composition can also include from about 25 to about 75 percent by weight of one or more solidifying agents. The solidifying agents may be selected from alkyl silicones, beeswax, C24-C28 alkyl dimethicone, C30 alkyl dimethicone, cetyl methicone, stearyl methicone, cetyl dimethicone, stearyl dimethicone, cerotyl dimethicone, candelilla wax, carnauba, cerasin, hydrogenated microcrystalline wax, jojoba wax, microcrystalline wax, lanolin wax, ozokerite, paraffin, cetyl esters and mixtures of such solidifying agents. The composition further includes from about 5 to about 20 percent by weight of one or more viscosity enhancers. The viscosity enhancers may be selected from ethylene/vinyl acetate copolymers, polyethylene, silica and mixtures of such viscosity enhancers. The composition may also include a rheology modifier for providing stability of insoluble and partially soluble components.
The articles with respect to this aspect of the invention may have compositions on at least a portion of the bodyfacing surface of the bodyside liner in which the compositions may have certain physical properties. For example, the compositions may have melting points of from about 32xc2x0 C. to about 100xc2x0 C. such that the compositions are relatively immobile on the bodyfacing surface at room temperature but are readily transferable to the skin at body temperature. The compositions may also have viscosities that range from about 10 to about 10,000 centipoise at a temperature of 60xc2x0 C. and a viscosity of from about 200 centipoise to about 100,000 centipoise at 55xc2x0 C. Additionally, the compositions may have a penetration hardness of from about 5 millimeters to about 365 millimeters at 25xc2x0 C. The compositions may be applied to at least a portion of the bodyfacing surface in an amount of from about 0.1 grams per meter squared (g/m2) to about 30 g/m2. Those of skill in the art will know how to modify the components and attributes of the compositions encompassed by the invention to achieve the desired skin barrier benefits based on the disclosure provided herein.
The present invention is further directed to a method of applying a composition to a bodyfacing surface of a bodyside liner of an absorbent article. The method of the invention includes a step of heating a composition to a temperature above the melting point of the composition. The composition can have a melting point of from about 32xc2x0 C. to about 100xc2x0 C. The composition can include a natural fat or oil, a sterol or sterol derivative, an emollient, a solidifying agent and a viscosity enhancer. The method further includes a step of applying the composition to the bodyfacing surface of a bodyside liner of an absorbent article. The bodyfacing surface is that surface of the absorbent article that comes into contact with the skin of the wearer of the absorbent article. Other components of the absorbent article besides the bodyside liner may come into contact with the skin of the wearer. The composition can also be applied to those components including the waist elastics, the leg elastics, containment flaps and any other components coming into contact with the skin.
The composition can be applied to the bodyfacing surface using a variety of techniques including foam application, spraying, slot coating, printing or combinations of these application techniques. The method of the invention also includes a step of resolidifying the composition. The composition can be resolidified in a variety of ways including chilling, slow cooling, curing or a combination of these techniques. Further, the composition can have a penetration hardness of from about 5 to about 365 millimeters at 25xc2x0 C. after the step of resolidification.
In another embodiment, the present invention is directed to a composition. While the composition may have other useful functions, the composition generally provides a benefit to the function of the skin barrier. The composition can include from about 0.1 to about 95 percent by weight of one or more natural fats or oils, or the composition can include a mixture of one or more natural fats and oils. The composition can also include from about 0.1 to about 10 percent by weight of one or more sterols, sterol derivatives or mixtures of both sterols and sterol derivatives. An additional component of the composition of the invention can be from about 1 to about 95 percent by weight of one or more emollients. The emollient(s) can act as a lubricant to reduce abrasiveness and help to maintain a soft, smooth and pliable appearance to the skin. The composition can further include from about 5 to about 95 percent by weight of one or more solidifying agents. The solidifying agent(s) can function as solidifiers or stabilizers for the emollient(s) and natural fats/oils of the composition, provide a tackiness to the composition that improves transfer properties and act as an occlusive agent, moisturizer or barrier enhancer. The composition of the invention can also include from about 1 to about 25 percent by weight of one or more viscosity enhancers. The viscosity enhancer(s) can modify the viscosity of the composition to improve the consistency of the composition for the purpose for which the composition is intended to be used.
The composition of the invention can have a melting point of from about 32xc2x0 C. to about 100xc2x0 C. depending on the function for which the composition is intended to be employed. If the composition is intended to be applied to an absorbent article, it may be desirable for the composition to have a melting point such that the composition is immobile at room temperature. Depending on the processing and handling to which the composition will be exposed, it may be beneficial for the composition to have a process viscosity less than about 100 centipoise under shear or pressure. Examples of specific compounds for the fat/oil, sterol/sterol derivative, emollient, solidifying agent and viscosity enhancer components of the composition can be as described previously and as will be described herein.
In an additional embodiment, the present invention is directed to a method for improving skin barrier function of a skin surface of a user. The method can include a step of contacting the skin surface of a user with a bodyfacing surface of a liner material. The liner material may be any type of woven or non-woven material. More specifically, the liner material is of a material that is typically used for the bodyside liner of an absorbent article. The bodyfacing surface of the liner material has a composition on it. The composition can include a natural fat or oil, a sterol or sterol derivative, an emollient, a solidifying agent and a viscosity enhancer. More specifically, the composition can include from about 0.1 to about 95 percent by weight of natural fats or oils, from about 0.1 to about percent by weight of sterols or sterol derivatives, from about 1 to about 95 percent by weight of emollients, from about 5 to about 95 percent by weight of solidifying agents and from about 1 to about 25 percent by weight of viscosity enhancers.
The method can also include a step of maintaining the bodyfacing surface of the liner material in contact with the skin surface of a user for a sufficient amount of time to transfer the composition to the skin surface. For purposes of the method, a sufficient amount of time would be the amount of time necessary for enough of the composition to have been transferred so as to enhance the skin barrier. The method of the invention further includes a step of repeating contact of the skin surface with the bodyfacing surface of the liner material for a sufficient amount of time in order to have an improvement in the skin barrier function of the wearer""s skin. The repeated contact can occur by either applying additional composition to the bodyfacing surface of the liner material or by applying a new liner material having a full amount of the composition on the bodyfacing surface.
The absorbent articles, methods and compositions of the invention advantageously enhance the skin barrier in such a way not observed with conventional absorbent articles and compositions. Consequently, use of the absorbent articles and compositions of the invention enhance the skin barrier to protect against damage caused by physical and biological irritations. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. The accompanying drawings, that are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the articles, methods and compositions of the invention. Together with the description, the drawings serve to explain the various aspects of the invention.